The present invention generally relates to a novel phosphatidylserine (PS) receptor, to homologues thereof, to nucleic acids encoding such a receptor and homologues thereof, to agonist and antagonist compounds that specifically associate with and affect the activation state of such a receptor, including antibodies, antibody fragments and binding partners that selectively bind to such a receptor, and to methods of making and using such a receptor, homologues thereof, and agonist and antagonist compounds of such a receptor.
The culmination of apoptosis in vivo is phagocytosis of cellular corpses. Of the numerous cells reported to recognize and remove apoptotic bodies, the macrophage is the most prominent. Apoptotic cells express cell surface changes which allow recognition and removal by macrophages. Removal occurs before lysis, which prevents the release of potentially toxic and immunogenic intracellular contents from the apoptotic cells into the surrounding tissue. Thus, in tissues such as the thymus in which apoptosis is ongoing, normal structure and function are maintained and inflammation is avoided. The removal of apoptotic cells also appears to be critical in the resolution of inflammation. Phagocytosis of apoptotic cells in inflammatory sites has been documented in vivo in experimental as well as clinical disease states, and disorders of apoptosis have been suggested to contribute to the persistence of chronic inflammatory conditions in the lung, kidney and other organs (Grigg et al., Lancet. 338:720-722, 1991; Cox et al., Am. J. Respir. Cell. Mol. Biol. 12:232-237, 1995; Haslett et al., Phil. Trans. R. Soc. Lond. B. 345:327-333, 1994).
During apoptosis, plasma membrane phospholipid asymmetry is lost, exposing phosphatidylserine (PS) externally (Fadok et al., J Immunol 148:2207-2216 (1992); Martin et al., J Exp Med 182:1545-1556 (1995); Verhoven et al., J Exp Med 182:1597-1601 (1995); van den Eijnde et al., Apoptosis 3:9-16 (1998)). Phagocytosis of apoptotic cells can be inhibited stereospecifically by PS and its structural analogues, but not by other anionic phospholipids, suggesting that PS is specifically recognized (Fadok et al., ibid.; Fadok et al., J Immunol 149:4029-4035 (1992); Fadok et al., J Immunol 151:4274-4285 (1993); Fadok et al., J Immunol 161:6250-6257 (1998); Pradhan et al., Mol Biol Cell 8:767-778 (1997); Bennett et al., Circ Res 77:1136-1142 (1995); Shiratsuchi et al., J Biol Chem 272:2354-2358 (1997)). However, prior to the present invention, the molecule responsible for PS recognition had not been positively identified.
Several potential candidates for PS recognition on apoptotic cells have been put forth, including CD36, CD68, CD14, and LOX-1 (Savill et al., J Clin Invest 90:1513-1522 (1992); Sambrano et al., Proc Natl Acad Sci U S A 92:1396-1400 (1995); Devitt et al., Nature 392:505-509 (1998); Oka et al., Proc Natl Acad Sci U S A 95:9535-9540 (1998)). In addition, xcex22GP1 may enhance uptake by bridging PS on the apoptotic cell to receptors on macrophages (Balasubramanian et al., J Biol Chem 272:31113-31117 (1997)). However, several observations suggest that receptors other than these scavenger/pattern recognition molecules must exist. These molecules do not appear to discriminate between PS and other anionic phospholipids including phosphatidylinositol (PI) (Oka et al., Proc Natl Acad Sci U S A 95:9535-9540 (1998); Rigotti et al., J Biol Chem 270:16221-16224 (1995); Wang et al., J Biol Chem 273:24309-24313 (1998); Ryeom et al., J Cell Sci 109:387-395 (1996); Shiratsuchi et al., J Biol Chem 274:5901-5908 (1999)), whereas uptake of apoptotic cells by PS-recognizing macrophages was not blocked by phosphatidylinositol (PI) or other anionic phospholipids (Fadok et al., J Immunol 148:2207-2216 (1992); Fadok et al., J Immunol 161:6250-6257 (1998)).
The removal of apoptotic cells is critical to normal tissue structure and function. In addition, one of the critical functions of the apoptotic cell when phagocytosed is to actively suppress macrophage proinflammatory functions. The nature and duration of the inflammatory response is determined to a large extent by competition between proinflammatory and anti-inflammatory uptake mechanisms. Disorders in either uptake or response to apoptotic cells by macrophages could contribute to chronic inflammation. Moreover, without being bound by theory, the present inventors believe that some pathogenic microorganisms and viruses may use the phosphatidylserine recognition pathway to gain entrance to a host cell. Also without being bound by theory, phosphatidylserine recognition may play a role in the ability of a tumor cell to avoid an immune response. Therefore, the ability to control cellular interactions which are mediated by phosphatidylserine recognition has multiple therapeutic benefits. Thus, there is a need in the art to identify and characterize the phosphatidylserine receptor.
The present invention generally relates to isolated phosphatidylserine receptor proteins, nucleic acid molecules, homologues thereof, agonist and antagonist compounds that specifically associate with and affect the activation state of such a receptor, and methods of making and using such a receptor, homologues thereof, and agonist and antagonist compounds of such a receptor.
One embodiment of the present invention relates to an isolated phosphatidylserine receptor protein selected from the group of: (a) a protein consisting essentially an amino acid sequence selected from the group consisting of: (i) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:3 to about position 414 of SEQ ID NO:3; (ii) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:5 to about position 403 of SEQ ID NO:5; (iii) an amino acid sequence spanning from between about positions 206 and 243 of SEQ ID NO:7 to about position 349 of SEQ ID NO:7; (iv) an amino acid sequence spanning from between about positions 257 and 294 of SEQ ID NO:9 to about position 408 of SEQ ID NO:9; and, (b) a homologue of the protein of (a), wherein the homologue consists essentially of an amino acid sequence that is at least about 70% identical, and more preferably at least about 80% identical, and more preferably at least about 90% identical, to the amino acid sequence of (a). The isolated phosphatidylserine receptor protein has a phosphatidylserine receptor biological activity. Preferably, such a protein consists essentially of an amino acid sequence selected from the group consisting of: (a) an amino acid sequence spanning from between about positions 289 of SEQ ID NO:3 to position 414 of SEQ ID NO:3; (b) an amino acid sequence spanning from between about positions 289 of SEQ ID NO:5 to position 403 of SEQ ID NO:5; (c) an amino acid sequence spanning from between about positions 243 of SEQ ID NO:7 to position 349 of SEQ ID NO:7; and (d) an amino acid sequence spanning from between about positions 294 of SEQ ID NO:9 to position 408 of SEQ ID NO:9. Particularly preferred phosphatidylserine receptor proteins in this embodiment include a protein that consists essentially of an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:3 to about position 414 of SEQ ID NO:3; and a protein that consists essentially of an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:5 to about position 403 of SEQ ID NO:3.
Another embodiment of the present invention relates to an isolated phosphatidylserine receptor protein selected from the group consisting of: (a) a protein comprising an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; and (b) a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical, and more preferably at least about 80% identical, and more preferably at least about 90% identical, to the amino acid sequence of (a), wherein the homologue is not SEQ ID NO:3. The isolated phosphatidylserine receptor protein has a phosphatidylserine receptor biological activity. In a preferred embodiment, the protein is selected from the group consisting of: SEQ ID NO:5 and a homologue of SEQ ID NO:5, wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical to SEQ ID NO:5. In a particularly preferred embodiment, the protein comprises an amino acid sequence selected from the group consisting of SEQ ID NO:5 and a fragment of at least about 316 amino acids of SEQ ID NO:5. In one aspect, the protein comprises an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, or SEQ ID NO:9. In one embodiment, the homologue comprises at least about 25 contiguous amino acid residues, and more preferably at least about 100 contiguous amino acid residues, of the amino acid sequence of (a). In a particularly preferred embodiment, the receptor protein is a soluble phosphatidylserine receptor.
Another embodiment of the present invention relates to an isolated phosphatidylserine receptor homologue, wherein the homologue comprises an amino acid sequence that is: (a) at least 316 amino acids in length; (b) at least about 70% identical to an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; and, (c) less than 100% identical to the amino acid sequence of (a). In this embodiment, the homologue is not SEQ ID NO:3, and the homologue has a phosphatidylserine receptor biological activity. Preferably, the amino acid sequence of the homologue differs from the amino acid sequence of (a) by at least one modification selected from the group consisting of an amino acid deletion, an amino acid insertion, and an amino acid substitution. In another aspect of this embodiment, the homologue is less than about 95% identical to the amino acid sequence of (a). In another aspect of this embodiment, the homologue is at least about 80% identical, and more preferably at least about 90% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Yet another embodiment of the present invention relates to an isolated phosphatidylserine receptor protein comprising an amino acid sequence that aligns with 100% identity at least 50% of the non-Xaa residues of SEQ ID NO:10, wherein the protein is not SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, or SEQ ID NO:9.
Also included in the present invention are fusion proteins that include any of the above-described phosphatidylserine receptor proteins, including homologues thereof, that are operatively linked to a heterologous protein sequence.
Another embodiment of the present invention relates to an isolated antibody, antigen binding fragment of such an antibody, or a binding partner, that selectively binds to any of the above-described phosphatidylserine receptor proteins, including homologues thereof. In a preferred embodiment, the antibody, antigen binding fragment, or binding partner, selectively binds to a protein consisting essentially of a fragment of SEQ ID NO:3 spanning from between about positions 252 and 289 of SEQ ID NO:3 and about position 414 of SEQ ID NO:3. In another preferred embodiment, the antibody, antigen binding fragment, or binding partner, selectively binds to a protein consisting essentially of a fragment of SEQ ID NO:5 spanning from between about positions 252 and 289 of SEQ ID NO:5 and about position 403 of SEQ ID NO:5.
Yet another embodiment of the present invention relates to a composition comprising at least about 1 xcexcg of an isolated phosphatidylserine receptor protein of the present invention. The protein is selected from the group consisting of: (a) a protein comprising an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; (b) a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical, and more preferably at least about 80% identical, and more preferably at least about 90% identical, to the amino acid sequence of (a); (c) a fragment of the protein of (a) consisting essentially an amino acid sequence selected from the group consisting of: (i) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:3 to about position 414 of SEQ ID NO:3; (ii) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:5 to about position 403 of SEQ ID NO:5; (iii) an amino acid sequence spanning from between about positions 206 and 243 of SEQ ID NO:7 to about position 349 of SEQ ID NO:7; (iv) an amino acid sequence spanning from between about positions 257 and 294 of SEQ ID NO:9 to about position 408 of SEQ ID NO:9 spanning from between about positions 252 and 289 of SEQ ID NO:3 and about position 414 of SEQ ID NO:3; and (d) a homologue of the protein of (c), wherein the wherein the homologue consists essentially of an amino acid sequence that is at least about 70% identical, and more preferably at least about 80% identical, and more preferably at least about 90% identical, to the amino acid sequence of (c). The isolated phosphatidylserine receptor protein has a phosphatidylserine receptor biological activity. In a preferred aspect of this embodiment, the protein consists essentially of an amino acid sequence selected from the group consisting of a fragment of at least about 316 amino acids of SEQ ID NO:3, and a fragment of SEQ ID NO:3 spanning from between positions 252 and 289 of SEQ ID NO:3 and position 414 of SEQ ID NO:3, wherein the protein has a phosphatidylserine biological activity. In one aspect, the homologue of (b) comprises at least about 25 contiguous amino acid residues of SEQ ID NO:3. In another aspect, the homologue of (b) comprises at least about 100 contiguous amino acid residues of SEQ ID NO:3. In a preferred embodiment, the protein comprises SEQ ID NO:3.
Yet another embodiment of the present invention relates to a composition comprising an isolated phosphatidylserine receptor protein selected from the group consisting of: (a) a protein comprising an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; (b) a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical to the amino acid sequence of (a); (c) a fragment of the protein of (a) consisting essentially an amino acid sequence selected from the group consisting of: (i) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:3 to about position 414 of SEQ ID NO:3; (ii) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:5 to about position 403 of SEQ ID NO:5; (iii) an amino acid sequence spanning from between about positions 206 and 243 of SEQ ID NO:7 to about position 349 of SEQ ID NO:7; (iv) an amino acid sequence spanning from between about positions 257 and 294 of SEQ ID NO:9 to about position 408 of SEQ ID NO:9 spanning from between about positions 252 and 289 of SEQ ID NO:3 and about position 414 of SEQ ID NO:3; and (d) a homologue of the protein of (c), wherein the wherein the homologue consists essentially of an amino acid sequence that is at least about 70% identical to the amino acid sequence of (c). The isolated, substantially purified phosphatidylserine receptor protein has a phosphatidylserine receptor biological activity. In this composition, at least about 80% weight/weight of total protein in the composition is the isolated phosphatidylserine receptor protein. Preferably, the phosphatidylserine receptor protein comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Another embodiment of the present invention relates to an isolated cDNA or RNA molecule selected from the group consisting of: (a) a nucleic acid sequence consisting essentially of nucleotides encoding an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; (b) a nucleic acid sequence encoding a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is between 316 and 414 amino acid residues in length and that is at least about 70% identical to the amino acid sequence of (a); (c) a nucleic acid sequence encoding a protein consisting essentially of a fragment of the amino acid sequence of (a) selected from the group consisting of: (i) a fragment spanning from between about positions 252 and 289 of SEQ ID NO:3 to about position 414 of SEQ ID NO:3; (ii) a fragment spanning from between about positions 252 and 289 of SEQ ID NO:5 to about position 403 of SEQ ID NO:5; (iii) a fragment spanning from between about positions 206 and 243 of SEQ ID NO:7 to about position 349 of SEQ ID NO:7; and (iv) a fragment spanning from between about positions 257 and 294 of SEQ ID NO:9 to about position 408 of SEQ ID NO: 9; (d) a nucleic acid sequence encoding a homologue of the protein of (c), wherein the wherein the homologue consists essentially of an amino acid sequence that is at least about 70% identical to the amino acid sequence of (c); and (e) a nucleic acid sequence that is fully complementary to the nucleic acid sequence of (a), (b), (c) or (d). In this embodiment, the nucleic acid sequence is preferably selected from the group consisting of SEQ ID NO:2, SEQ ID NO:4, SEQ ID NO:6 and SEQ ID NO:8. In a particularly preferred embodiment, the nucleic acid sequence is SEQ ID NO:2. In another aspect, the nucleic acid sequence consists essentially of from between nucleotide 756 and nucleotide 867 of SEQ ID NO:2 to nucleotide 1242 of SEQ ID NO:2.
Yet another embodiment of the present invention relates to an isolated cDNA or RNA molecule selected from the group consisting of: (a) a nucleic acid sequence encoding a protein comprising an amino acid sequence selected from the group consisting of SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; (b) a nucleic acid sequence encoding a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical to the amino acid sequence of (a), wherein the homologue is not SEQ ID NO:3; (c) a nucleic acid sequence encoding a protein consisting essentially of a fragment of the amino acid sequence of (a) selected from the group consisting of: (i) a fragment spanning from between about positions 252 and 289 of SEQ ID NO:5 to position 403 of SEQ ID NO:5; (ii) a fragment spanning from between about positions 206 and 243 of SEQ ID NO:7 to position 349 of SEQ ID NO:7; and, (iii) a fragment spanning from between about positions 257 and 294 of SEQ ID NO:9 to position 408 of SEQ ID NO:9; (d) a nucleic acid sequence encoding a homologue of the protein of (c), wherein the wherein the homologue consists essentially of an amino acid sequence that is at least about 70% identical to the amino acid sequence of (c); and (e) a nucleic acid sequence that is fully complementary to the nucleic acid sequence of (a), (b), (c) or (d). In one aspect, the nucleic acid sequence is selected from the group consisting of SEQ ID NO:4, SEQ ID NO:6 and SEQ ID NO: 8. In a preferred embodiment, the nucleic acid sequence comprises SEQ ID NO:4. In another embodiment, the nucleic acid sequence consists essentially of from between nucleotide 756 and nucleotide 867 of SEQ ID NO:4 to nucleotide 1209 of SEQ ID NO:4.
Also included in the present invention are recombinant nucleic acid molecules consisting of any of the above-described isolated cDNA or RNA molecules and a nucleic acid sequence that is heterologous to the isolated cDNA or RNA molecule. In one aspect, the heterologous nucleic acid sequence is an expression vector. Another embodiment of the present invention relates to a recombinant cell that expresses any of the recombinant nucleic acid molecules described herein.
Yet another embodiment of the present invention relates to a method to identify a regulator of a phosphatidylserine receptor. Such a method includes a first step of: (a) contacting a phosphatidylserine receptor protein with a putative regulatory compound, wherein the phosphatidylserine receptor protein is selected from the group consisting of: (i) a protein comprising an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9; (ii) a homologue of the protein of (a), wherein the homologue comprises an amino acid sequence that is at least 316 amino acid residues in length and that is at least about 70% identical to the amino acid sequence of (a); (iii) a protein consisting essentially of a fragment of the amino acid sequence of (a) selected from the group consisting of: (1) a fragment spanning from between about positions 252 and 289 of SEQ ID NO:3 to position 414 of SEQ ID NO:3; (2) a fragment spanning from between about positions 252 and 289 of SEQ ID NO:5 to position 403 of SEQ ID NO:5; (3) a fragment spanning from between about positions 206 and 243 of SEQ ID NO:7 to position 349 of SEQ ID NO:7; and, (4) a fragment spanning from between about positions 257 and 294 of SEQ ID NO:9 to position 408 of SEQ ID NO:9; and, (iv) a homologue of the protein of (iii), wherein the homologue comprises an amino acid sequence that is at least about 70% identical to the amino acid sequence of (iii). The phosphatidylserine receptor protein has a phosphatidylserine receptor biological activity. Such a method further includes the steps of: (b) detecting whether the putative regulatory compound binds to the receptor; and, (c) detecting whether the putative regulatory compound increases or decreases activity of the receptor as compared to prior to contact with the compound. Compounds that bind to the receptor and increase or decrease activity of the receptor, as compared to a receptor in the absence of the compound, indicates that the putative regulatory compound is a regulator of the phosphatidylserine receptor.
In this embodiment, the step of detecting whether the putative regulatory compound increases or decreases activation of the receptor can include, but is not limited to, the steps of contacting the receptor with a stimulator of the receptor and detecting whether activation of the receptor is increased or decreased in the presence of the putative regulatory compound as compared to in the absence of the putative regulatory compound. In one aspect, the method further comprises a step of detecting whether the putative regulatory compound regulates a biological activity of a cell that expresses the receptor, the biological activity being selected from the group consisting of transforming growth factor xcex2 (TGFxcex2) production, prostaglandin E2 (PGE2) production, tumor necrosis factor xcex1 (TNFxcex1) production, chemokine production, granulocyte-macrophage colony stimulating factor (GM-CSF) production, interleukin-1 (IL-1) production, phosphorylation of the receptor, and phagocytosis of apoptotic cells.
Another embodiment of the present invention relates to a method to stimulate or increase the activity of a phosphatidylserine receptor. Such a method includes the step of contacting a phosphatidylserine receptor with an agonist of the phosphatidylserine receptor, wherein the agonist increases the activity of the phosphatidylserine receptor, and wherein the receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9. Preferably, the agonist is selected from the group consisting of: an antibody that selectively binds to and activates the phosphatidylserine receptor, an antigen binding fragment that selectively binds to and activates the phosphatidylserine receptor, a binding partner that selectively binds to and activates the phosphatidylserine receptor, phosphatidylserine, and a product of drug design that increases the activity of the receptor as compared to in the absence of the product. In one aspect, the agonist is an antibody that selectively binds to and activates the receptor. In another aspect, the agonist increases production of a factor selected from the group consisting of transforming growth factor xcex2 (TGFxcex2) and prostaglandin E2 (PGE2) by cells in the subject. In another aspect, the agonist decreases production of a factor selected from the group consisting of tumor necrosis factor xcex1 (TNFxcex1), a chemokine, granulocyte-macrophage colony stimulating factor (GM-CSF), and interleukin-1 (IL-1) by in the subject. Preferably, the phosphatidylserine receptor is expressed by a cell selected from the group consisting of a macrophage, a fibroblast, a dendritic cell, a tumor cell, an epithelial cell and an endothelial cell. In one aspect, the agonist reduces inflammation in a patient.
Another embodiment of the present invention relates to a method to reduce the production of inflammatory cytokines by cells in a subject. This method includes the step of contacting the cells that express a phosphatidylserine receptor with an agonist of a phosphatidylserine receptor, wherein the agonist increases the activity of a phosphatidylserine receptor, and wherein the receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Yet another embodiment of the present invention relates to a method to promote survival of a transplanted cell or graft, comprising administering to a transplant recipient an agonist of a phosphatidylserine receptor, wherein the agonist increases the activity of a phosphatidylserine receptor, and wherein the receptor comprises an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Another embodiment of the present invention relates to a method to treat an autoimmune disease, comprising administering to a subject that has an autoimmune disease an agonist of a phosphatidylserine receptor, wherein the agonist increases the activity of a phosphatidylserine receptor, and wherein the receptor comprises an amino acid sequence selected from the group consisting of SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Yet another embodiment of the present invention relates to a method to reduce the activity of a phosphatidylserine receptor, comprising contacting a phosphatidylserine receptor with an antagonist of the phosphatidylserine receptor, wherein the antagonist decreases the activity of the phosphatidylserine receptor, and wherein the receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9. Preferably, the antagonist is selected from the group consisting of an antibody that reduces the activity of the receptor, an antigen binding fragment that reduces the activity of the receptor, a binding partner that reduces the activity of the receptor, a product of drug design that reduces the biological activity of the receptor, an anti-sense nucleic acid molecule that binds to a nucleic acid molecule encoding the receptor, a ribozyme that is specific for PS receptor RNA, and a soluble phosphatidylserine receptor. In a preferred embodiment, the antagonist is an antibody that selectively binds to the receptor and reduces the activity of the receptor. In one embodiment, the antagonist is a soluble phosphatidylserine receptor comprising an amino acid sequence selected from the group consisting of: (a) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:3 to position 414 of SEQ ID NO:3; (b) an amino acid sequence spanning from between about positions 252 and 289 of SEQ ID NO:5 to position 403 of SEQ ID NO:5; (c) an amino acid sequence spanning from between about positions 206 and 243 of SEQ ID NO:7 to position 349 of SEQ ID NO:7; (d) an amino acid sequence spanning from between about positions 257 and 294 of SEQ ID NO:9 to position 408 of SEQ ID NO:9; and, (e) an amino acid sequence that is a homologue of the amino acid sequence of (a), (b), (c), or (d), wherein the wherein the homologue amino acid sequence consists essentially of an amino acid sequence that is at least about 70% identical to the amino acid sequence of (a), (b), (c), or (d). The homologue has a phosphatidylserine receptor biological activity.
Another embodiment of the present invention is a method to reduce the association of an apoptotic tumor cell with a phosphatidylserine receptor expressed on the surface of bystander tumor cells, macrophages or dendritic cells, comprising contacting tumor cells of a patient with an antagonist of a phosphatidylserine receptor, wherein the antagonist decreases the activity of the phosphatidylserine receptor, and wherein the phosphatidylserine receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9.
Yet another embodiment of the present invention is a method to inhibit the infection of a host cell by a parasite, comprising contacting the host cell with an antagonist of a phosphatidylserine receptor, wherein the antagonist decreases the activity of the phosphatidylserine receptor, and wherein the phosphatidylserine receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9. Preferably, the parasite is selected from the group consisting of Trypanosomes and Leishmania.
Another embodiment of the present invention relates to a method to inhibit viral infection of host cells, comprising contacting the host cell with an antagonist of a phosphatidylserine receptor, wherein the antagonist decreases the activity of the phosphatidylserine receptor, and wherein the phosphatidylserine receptor comprises an amino acid sequence selected from the group consisting of: SEQ ID NO:3, SEQ ID NO:5, SEQ ID NO:7, and SEQ ID NO:9. Preferably, the viral infection is by a Herpes virus, and even more preferably, by a cytomegalovirus.